When a UE seeks to either discover or be discovered, a ProSe or D2D discovery process is often required. A ProSe discovery process is a process that identifies whether a ProSe-enabled discoverer UE is in the proximity of another ProSe-enabled discoveree UE, with or without the assistance of an Evolved Packet Core (EPC) which is considered a core network for the case of a Long Term Evolution (LTE) communication system. Said network assistance may or may not involve the Evolved Universal Terrestrial Radio Access Network (E-UTRA). Whenever a UE meets the proximity criteria relative to another UE, the UE can be said to be in proximity of another UE. The proximity criteria could involve at least a specific distance or a certain communication range class and could be different for the discovery process and any subsequent communication phase.
When the ProSe discovery process occurs in the EPC-level, the ProSe discovery process would involve a discovery procedure by which the EPC determines the proximity of two ProSe-enabled UEs and informs is them of their proximity. Prose-enabled UEs refers to UEs that support the current ProSe requirement and associated procedures [Reference 3GPP TS 23.278]. A Prose-enabled UE could also be a non-public safety UE e.g., a UE with commercial applications, a public safety UE, or both. Each ProSe-enabled UE may have a range class, which is a rough indication of distance for use in ProSe Discovery, for example, based on geographical distance, radio conditions.
A ProSe discovery process may involve different types of identifiers (ID). An EPC ProSe user ID is an identifier for EPC-level ProSe discovery and EPC support of WLAN direct communication to uniquely identify a UE registered for ProSe. This identifier could occasionally be reassigned by the ProSe Function in an EPC network. A ProSe Function ID is a fully qualified domain name (FQDN) that uniquely identifies a ProSe Function. An application ID is a globally unique identifier that identifies a specific application. An application Layer User ID is an identifier that identifies a user within the context of specific application. A wireless local area network (WLAN) Link Layer ID is a link layer identity that is used for WLAN direct discovery and/or WLAN direct communication. The WLAN Link Layer ID could be temporary such as a temporary MAC address or could be permanent such as a permanent MAC address.
D2D Communication, Proximity Communication, or ProSe Communication is a new feature that is currently being developed within the third generation partnership project (3GPP) as part of Release-12 and Release-13. There could be at least two main approaches for Proximity discovery—EPC-level ProSe discovery and ProSe Direct discovery. Both discoveries may be complementary solutions but can also be implemented independently. FIG. 1 illustrates an exemplary network architecture by which an EPC-level discovery is processed. The entities could involve a first UE 101 and a second UE 102 which would both be capable of ProSe applications or could both be ProSe-enabled. The entities may also involve the E-UTRAN 103. The ProSe Function 104 stands for D2D or ProSe functions collectively supported by an EPC network. The E-UTRAN 103 would be connected to a mobility management entity (MME) 105 the E-UTRAN 103 may also connect directly to a ProSe Function 104 within the EPC. The ProSe Function 104 would be connected to a Secured User Plane Location Platform (SLP) 106 through which location information could be obtained or approximated. The ProSe Function 104 could be connected to a ProSe application server 107 that could be a third party server and not an inherent part of the EPC network. Specific descriptions of the aforementioned entities are described by at least 3GPP technical specification (TS) 23.303 which are incorporated by reference and thus will not be repeated.
FIG. 2 shows a typical call flow of EPC-level ProSe discovery as utilized in a draft standard such as 3GPP TR 23.703 v1.0.0 which is incorporated by reference. The steps shown in FIG. 2 are to be briefly described as follows. In step S201, UE A would be assumed to perform UE registration for ProSe communication with the Prose Function A residing in their respective home public land mobile networks (Home PLMNs). In step S202, UE B would perform in UE registration for ProSe with the ProSe Function B residing in their respective Home PLMNs. Similarly, in steps S203 & S204, UE A and UE B would perform a ProSe application registration with ProSe Function A and ProSe Function B respectively in their Home PLMNs. In step S205, UE A would make a proximity request for UE B and receive an appropriate response in return. For example, if UE B is in the proximity of UE A within a predefined window of time, then UE A might be alerted for the presence of UE B. In response to the proximity request, ProSe Function A would request for a location update for UE A and for UE B. The location updates could be periodic or could be based on a triggered event or both. In order to request location updates for UE A, ProSe Function A would contact the SUPL Location Platform (SLP) A. Likewise, in order to request a location update for UE B, ProSe Function A would contact ProSe Function B, which would in turn request a location update for UE B from SLP B.
In step 206, ProSe Function A receives a report of the location of UE A from SLP A. In step S207, ProSe Function B receives a report of the location of UE B from SLP B. The locations of UE A and UE B could be reported to their respective ProSe Functions intermittently. ProSe Function B may forward the updates of location of UE B to ProSe Function A based on conditions set by ProSe Function A. Also, whenever ProSe Function A receives location updates for UE A and/or UE B, Prose Function A may perform proximity analysis for the locations of UE A and UE B. In step S208, when ProSe Function A detects that UE A and UE B are in proximity, ProSe Function A would informs UE A that UE B is in proximity and may optionally provide UE A with an assistance information for WLAN direct discovery and communication with UE B. Likewise, ProSe Function A would also inform ProSe Function B, which in turn would inform UE B of the detected proximity of UE A. The Prose Function B may also optionally provide UE B with an assistance information for WLAN direct discovery and communication with UE A.